Very simple design but hopefully save someone else the trouble. This is a clip to hold a sun blind in place on the rear windows of a car. I secured it with double-sided foam tape designed to affix licence plates. 3M VHB should also work. Just make sure the surface is clean of grease.
PLA should be OK depending on the temperature reached inside your car doesn't hit the glass temperature of PLA (60-65 C). I went for ABS, as I had some available in black and the small size of the part limited the chance of warping.
I printed at 100% infill but it isn't really a load bearing part so 20%+ most likely fine.